The present invention relates to a process and a generator for generating atomic iodine in the fundamental state, and it relates also to an iodine chemical laser employing such a process and such a generator.
Atomic iodine in the fundamental state finds employment in iodine chemical lasers. In lasers of this type known at present, the atomic iodine in the fundamental state necessary for the generation of the laser phenomenon is obtained by the transfer of electron energization from oxygen to iodine according to the following operation. Chlorine is injected under reduced pressure (some millibars) into concentrated hydrogen peroxide H.sub.2 O.sub.2 (for example 85%), in a basic medium. There results the continuous production of molecular oxygen in the singlet state O.sub.2.sup.1 .DELTA., which is a metastable chemical species whose life span, under reduced pressure, is sufficient to enable its transportation in ducts. It is thus possible to conduct it first to a cryogenic trap where water coming from the evaportation of the basic solution of H.sub.2 O.sub.2 is retained in part, then to an area of mixing with molecular iodine. The injection of molecular iodine into the flow of O.sub.2.sup.1 .DELTA. is accompanied by the dissociation of the molecular iodine I.sub.2 into atomic iodine in the fundamental state I.sub.2 p.sub.3/2 and the electron energization of the atomic iodine I.sub.2 p.sub.3/2 into atomic iodine in the I.sub.2 p.sub.1/2 state, which has the required properties to lead to a laser effect with a wavelength of 1.315.mu..
The dissociation of the molecular iodine into fundamental atomic iodine, the excitation of the fundamental atomic iodine into energized atomic iodine and, the obtaining of the laser radiation may be shown by the following diagram: ##STR1## In this diagram (R.sub.1) to (R.sub.5) represent the following chemical reactions: ##STR2## in which: I* represents energized atomic iodine I.sub.2 p1/2
I*.sub.2 represents a form of vibrationally energized molecular iodine, PA1 O.sub.2.sup.3 .SIGMA. represents the fundamental oxygen, PA1 h.gamma. represents a photon with the wavelength of 1.315.mu., PA1 K is the velocity constant associated with the reaction concerned. PA1 the combustible supporter is selected from among F.sub.2 and NF.sub.3 ; PA1 the fuel is selected from among HI, CF.sub.3 I, C.sub.3 F.sub.7 I, I.sub.2 and CHI.sub.3 ; PA1 the richness .phi. of the iodine compound with respect to the stoichiometric proportions is 0.5&lt;.phi.&lt;2.5 by using the combustion supporter F.sub.2 and 0.6&lt;.phi.&lt;2.6 by using the combustion supporter NF.sub.3 ; PA1 and the said combustion reaction is made under a pressure condition between 50 torrs and 5 bars. PA1 the combustion supporter is NF.sub.3 and the fuel is HI with 0.6&lt;.phi.&lt;2 and 3.24&lt;m&lt;10.81; PA1 the combustion supporter is NF.sub.3 and the fuel is CF.sub.3 I with 0.6&lt;.phi.&lt;1.3 and 4.96&lt;m&lt;10.77; PA1 the combustion supporter is NF.sub.3 and the fuel is C.sub.3 F.sub.7 I with 0.6&lt;.phi.&lt;1.3 and 1.50&lt;m&lt;3.25; PA1 the combustion supporter is NF.sub.3 and the fuel is I.sub.2 with 1.7&lt;.phi.&lt;2.3 and 9.12&lt;m&lt;12.34; PA1 the combustion supporter is NF.sub.3 and the fuel is CHI.sub.3 with 0.8&lt;.phi.&lt;21.2 and 2.66&lt;m&lt;4; PA1 the combustion supporter is F.sub.2 and the fuel is HI with 0.5&lt;.phi.&lt;2.2 and 3.36&lt;m&lt;14.82; PA1 the combustion supporter is F.sub.2 and the fuel is CF.sub.3 I with 0.5&lt;.phi.&lt;1.3 and 5.15&lt;m&lt;13.41; PA1 the combustion supporter is F.sub.2 and the fuel is C.sub.3 F.sub.7 I with 0.5&lt;.phi.&lt;1.3 and 1.56&lt;m&lt;4.06; PA1 the combustion supporter is F.sub.2 and the fuel is I.sub.2 with 1.5&lt;.phi.&lt;2.5 and 10.02&lt;m&lt;16.71; PA1 the combustion supporter is F.sub.2 and the fuel is CHI.sub.3 with 0.6&lt;.phi.&lt;1.3 and 2.49&lt;m&lt;5.39. PA1 a combustion chamber possessing two injectors to deliver respectively a fuel and a combustion supporter, means for initiating combustion of the fuel-combustion supporter mixture, and a supersonic outlet duct to collect the products emerging from the combustion; PA1 first means for conducting a fuel in regulatable amount and speed to one of the injectors; and PA1 second means to conduct a combustion supporter in regulatable amount and speed to the other injector; and PA1 one at least of the fuel and of the combustion supporter being an iodine compound in excess with respect to the stoichiometric proportions corresponding to the above-said combustion reaction in order that atomic iodine in the fundamental state may be present in the products emerging from the combustion, and in which: the combustible supporter is selected from among F.sub.2 and NF.sub.3 ; the fuel is selected from among HI, CF.sub.3 I, C.sub.3 F.sub.7 I, I.sub.2 and CHI.sub.3 ; the richness .phi. of the iodine compound with respect to the stoichiometric proportions is 0.5&lt;.phi.&lt;2.5 by using the combustible supporter F.sub.2 and 0.6&lt;.phi.&lt;2.6 by using the combustion supporter NF.sub.3 ; and the said combustible reaction is made under a pressure condition between 50 torrs and 5 bars.
This model shows that the step of dissociation of the molecular iodine into atomic iodine is a fundamental step, caused by a slow chemical reaction (R.sub.3) which penalizes the emission of the laser radiation.
In addition, it is known that the water present in the O.sub.2.sup.1 .DELTA. is a deactivator of I* and I.sub.2 *: (R.sub.6) I.sub.2 *H.sub.2 O.fwdarw.I.sub.2 ; H.sub.2 O; K(R.sub.6)=3.times.10.sup.-10 cm.sup.3 molec.sup.-1 s.sup.-1 ; (R.sub.7) I*+H.sub.2 O.fwdarw.I+H.sub.2 O; K(R.sub.7)=2.3.times.10.sup.-12 cm.sup.3 molec.sup.-1 s.sup.-1.
An important drawback of this known process is hence to necessitate the presence of cryogenic traps designed to remove, at least in large part, the water which accompanies the singlet oxygen flow O.sub.2.sup.1 .DELTA., which cryogenic traps raise the expense and increase the complexity of the invention.
Another drawback, not less important, is that the molecular iodine is a chemical species whose physical properties render the use very delicate. It is in addition very difficult to obtain high and reproducible flow rates and the inevitable presence of solid particles of iodine pollutes the laser cavity.